Isolation tools are used in hydrocarbon wells for a variety of purposes. They are commonly run in a well near the end of a tubing string and below a hydraulically set packer to isolate the packer from formation pressure and allow hydraulic operations above the isolation tool. They are run on the end of tubing strings or in order to pressure test the made up string. They are occasionally run on the bottom of casing strings before cementing the string in a well bore. Other uses will be apparent to those skilled in the art.
One type isolation tool comprises a pair of oppositely facing curved ceramic discs shown in U.S. Pat. No. 5,924,696. These discs have a strong side and a weak side, i.e. the convex side can resist considerably higher pressures than the concave side. These discs are arranged with the convex side facing toward the pressure to be resisted, i.e. the upper disc has its convex side facing upwardly and the lower disc has its convex side facing downwardly.
The upper ceramic disc disclosed in this patent is broken by dropping a weight or go-devil into the tubing string so this device is mainly usable in vertical wells.
It is desirable to provide an isolation tool comprising one or more ceramic domes which are usable in the horizontal or vertical leg of a hydrocarbon well. Such devices are shown in U.S. Pat. No. 7,806,189 and U.S. Printed Patent Application 20110017471 and application Ser. No. 12/800,622 which are incorporated herein by reference.
Other disclosures of interest are found in U.S. Pat. Nos. 3,831,680; 4,510,994; 4,658,902; 5,511,617; 6,155,350; 6,672,389; 7,044,230; 7,210,533 and 7,350,582 and U.S. Printed Patent Applications 20070074873; 20080271898; 20090056955; 20090020290 and 20120125631.